低孔隙水压力对砂岩卸荷力学特性影响研究

发布时间：2018-08-30 11:21

【摘要】：为了研究低孔隙水压力对砂岩卸荷力学特性的影响,在TOP INDUSTRIE多功能岩石三轴测试系统上,设计进行不同围压(5,10,15,20 MPa)和不同孔隙水压力(0,0.3,0.6,0.9,1.2 MPa)下的砂岩三轴卸荷试验。重点分析孔隙水压力对砂岩卸荷强度及变形破坏特征的影响。研究结果表明:(1)随着孔隙水压力的增大,岩样加载阶段的弹性模量逐渐减小,而且围压越小,相同的孔隙水压力增量条件下,弹性模量减小趋势越明显;(2)在卸载过程中,岩样侧向变形的增大速率明显大于轴向变形,而且,孔隙水压力越大,围压越小,侧向扩容现象越明显,岩样越容易破坏;(3)在卸载过程中,岩样的变形模量呈现先缓后陡的劣化规律,而且围压越小、孔隙水压力越大,变形模量降低幅度越大;(4)随着孔隙水压力的增大,岩样破坏时对应的围压值逐渐增大,黏聚力和内摩擦角降低趋势明显,说明孔隙水压力加速了岩石破坏的进程;(5)水对砂岩矿物颗粒的软化和颗粒间连接的弱化作用,以及孔隙水压力的水楔效应,是导致砂岩卸荷力学特性劣化的根本原因。因此,在涉水工程岩体卸荷变形稳定分析中,孔隙水压力的作用效应不容忽视。
[Abstract]:In order to study the effect of low pore water pressure on the unloading mechanical properties of sandstone, triaxial unloading tests of sandstone under different confining pressures (5 ~ 10 ~ 1520 MPa) and different pore water pressures (0 ~ 0.36 ~ 0.6 ~ 0.91.2 MPa) were designed on TOP INDUSTRIE multifunctional rock triaxial test system. The influence of pore water pressure on unloading strength and deformation and failure characteristics of sandstone is analyzed. The results show that: (1) with the increase of pore water pressure, the elastic modulus of rock samples decreases gradually, and the smaller the confining pressure, the more obvious the decreasing trend of elastic modulus is under the same pore water pressure increment condition; (2) in the unloading process, The increasing rate of lateral deformation of rock sample is obviously larger than that of axial deformation. Moreover, the larger the pore water pressure, the smaller the confining pressure, the more obvious the lateral expansion phenomenon is, and the easier the rock sample is to destroy. (3) during unloading, The deformation modulus of rock samples shows the law of deterioration first slowly and then steeply, and the smaller the confining pressure, the greater the pore water pressure, the greater the decrease of deformation modulus; (4) with the increase of pore water pressure, the confining pressure corresponding to rock sample failure increases gradually. The decreasing trend of cohesion and internal friction angle shows that pore water pressure accelerates the process of rock failure, (5) the softening of sandstone mineral particles and the weakening of intergranular connection by water, and the water wedge effect of pore water pressure. It is the fundamental cause of the degradation of the unloading mechanical properties of sandstone. Therefore, in the stability analysis of unloading deformation of wading engineering, the effect of pore water pressure can not be ignored.
【作者单位】：三峡大学三峡库区地质灾害教育部重点实验室;
【基金】：国家自然科学基金资助项目(51679127);国家自然科学基金重点项目(51439003) 湖北省自然科学基金重点项目(2015CFA140)~~
【分类号】：TU45

【相似文献】